The teenage killer was forced to supply drugs from the age of 11 and had previously been part of a county lines operation.
He was also obsessed with knives, having stored more than 600 images of blades on his phone and viewed news stories about fatal stabbings.
On 21 June last year, he ambushed 39-year-old Darren Edginton in the St Paul’s area of Bristol and plunged a knife into his chest.
The boy was convicted of manslaughter after a trial last year and on Friday was jailed for four years and six months with a two-year extended licence period.
“This was a wicked crime,” said judge Peter Johnson when sentencing him at Bristol Crown Court.
“The almost casual way in which you, a 14-year-old boy, carried out the stabbing in cold blood in broad daylight, in a public place, is chilling.”
The judge said the boy had a “keen interest, if not obsession with knives” at the time of his dispute with Mr Edginton.
“You have a deeply ingrained habit of carrying a knife. You were prepared to stab someone over a trivial matter, “ he added.
The teenager had argued with Mr Edginton about a “YoBike” dockless bicycle outside a shop in Grosvenor Road, Bristol, at around 5.40pm.
A witness heard the boy say “I’m going to kill”, while others in his group of friends shouted “let’s do it”.
Minutes later the boy stabbed Mr Edginton after leading him into nearby Winkworth Place.
“You went round the corner with a place you knew there was no CCTV, planning to ambush Mr Edginton with the knife you were carrying,” the judge told him.
“When Mr Edginton came round the corner, you stabbed him in the chest.”
Mr Edginton died a short time later from a stab wound to his chest. He was described by his family in court as a “kind caring man” and “a much loved father and son”.
Detectives said the boy was “one of the youngest people ever to be convicted of manslaughter in the Avon and Somerset force area.”
Avon and Somerset Police and Crime Commissioner Sue Mountstevens said: “This tragic case reinforces the need for a public health approach to tackle knife crime and serious violence in order to keep our communities safe.
“We need to be taking action to provide interventions for young people at a much earlier stage and identify the root causes of such terrible offences that have a devastating impact on individuals, families and our neighbourhoods.”
Additional reporting by Press Association